Method for preventing bottom water coning in oil wells

ABSTRACT

Petroleum hydrocarbons are produced from a formation which is in contact and overlays a water-producing formation by a process in which water coning is inhibited. In this process a liquid hydrocarbon at a temperature of about 200* to 500* F is injected via a well bore into the lower portion of the producing formation, the liquid hydrocarbon is withdrawn via the well bore from the upper portion of the producing formation and is continuously injected and withdrawn while at the same time, petroleum hydrocarbons are produced from the upper portion of the said hydrocarbon-bearing formation. Prior to the injection of the hot hydrocarbon liquid, a slug of carbon dioxide or flue gases which can optionally contain a hydrolyzable silane, may be injected into the upper portion of the formation.

9 Allen 1 Nov. 5, 1974 1 1 METHOD FOR PREVENTING BOTTOM WATER CONlNG [NOIL WELLS [75] Inventor: Joseph C. Allen, Bellaire, Tex.

[73] Assignee: Texaco, Inc., New York, NY.

[22] Filed: Mar. 14, 1973 [21] Appl. N0.: 340,994

[52] US. Cl. 166/303, l66/306 [51] Int. Cl E21b 43/24, EZlb 43/16 [58]Field of Search 166/303, 306, 272

[56] 1 References Cited UNITED STATES PATENTS 2,788,855 4/1957 Peterson166/303 2,832,416 4/1958 Allen r 166/306 2.862.558 12/1958 Dixon v166/272 2876,8313 3/1959 Williamsi v 166/272 $294,167 12/1966 Vogel166/306 3349,8511 10/1967 Schlicht et a1. 166/303 Primary ExaminerJamcsA. Leppink Attorney, Agent, or FirmThomas H. Whaley; C .G. Ries [57]ABSTRACT producing formation by a process in which water coning isinhibited. 1n this process a liquid hydrocarbon at a temperature ofabout 200 to 500 F is injected via a well bore into the lower portion ofthe producing formation, the liquid hydrocarbon is withdrawn via thewell bore from the upper portion of the producing for mation and iscontinuously injected and withdrawn while at the same time, petroleumhydrocarbons are produced from the upper portion of the saidhydrocarbon-bearing formation. Prior to the injection of the hothydrocarbon liquid, a slug of carbon dioxide or flue gases which canoptionally contain a hydrolyzable silane, may be injected into the upperportion of the fomiation.

3 Claims, 2 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of theInvention v This invention relates to the production of petroleumhydrocarbon from a subsurface reservoir. More particularly, thisinvention relates to the production of petroleum hydrocarbons andespecially to heavy hydrocarbon oils from a subsurface reservoir whichis in contact with and overlays-a substantially water-saturated porousformation. This invention also relates to a method for overcoming waterconing which sometimes results during production of hydrocarbons fromsuch formations.

2. Prior Art Water coning is a term given to the mechanism underlyingthe entry of bottom waters into producing wells. Petroleum hydrocarbbonsare often produced from porous subsurface formations which overlay asubstantially water-saturated porous formation. Under static conditionsthe water, being of greater density than the hydrocarbons, remainsbeneath and at the bottom of the hydrocarbon-producing formation. Athigh rates of production of petroleum hydrocarbons, however, the upperboundary or surface of the substantially water-saturated formation risesdue to the increased flow into the liquid petroleum-producing formationimmediately adjacent and above the substantially watersaturatedformation. The rise of water into the hydrocarbon-producing formationand into the well bore represents a dynamic effect in which the upwarddirected pressure gradients associated with the flow of the hydrocarbonsinto the producing well bore are able to balance the hydrostatic head ofthe resulting elevated water column.

Various methods have been suggested heretofore to eliminate or to reducethe water-coning phenomenon. These methods have included reducing thewell penetration into the hydrocarbon-producing formation so that higherproduction rates are possible without at the same time experiencing arelatively increased production of water therewith. Another method whichhas been suggested is to bottom the producing well into a substantiallywater-impermeable formation. These indicated methods. however, cannot besuccessfully employed in all instances to eliminate or reducewaterconing. Certain underground hydrocarbon-producing formations areonly a relatively few feet in thickness. Accordingly, reducing the wellbore penetration into such a formation would unduly restrict therecovery of petroleum hydrocarbons therefrom. Otherhydrocarbon-producing formations do not have associated therewith animmediately underlying waterimpermeable formation.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to a method ofproducing petroleum hydrocarbons and inhibiting water coning during theproduction of petroleum hydrocarbons from a well bore which penetrates asurface petroleum hydrocarbon-producing formation which is in contactwith and overlaysan adjacent water-producing formation which comprises:

a. injecting via said well bore a liquid hydrocarbon at a temperature ofabout 200 to about'500 F into injection, which is conveniently the wellbore itself. Inithe lower part of said hydrocarbon-producing formation,

b. withdrawing via said well bore the injected liquid hydrocarbon fromthe upper portion of the hydrocarbon-producing formation, and

c. continuously injecting and withdrawing said liquid hydrocarbon whileat the same time producing via said well bore petroleum hydrocarbonsfrom the upper portion of the said hydrocarbon-bearing formation, thevolume of the liquid hydrocarbon injected being less than the volume ofthe withdrawn liquid hydrocarbon plus the volume of the producedpetroleum hydrocarbons, the volumes being expressed in reservoir orformation volumes.

DETAILED DESCRIPTION OF THE INVENTION The operation of this inventionwill become apparent with reference to the accompanying drawing wherein:

FIG. 1 schematically illustrates the water-coning phenomenon; and

FIG. 2 schematically illustrates a method in accordance with thisinvention for overcoming water coning.

continued until the water has been displaced a substantial radialdistance, e.g., at least about 5 feet, preferably at least 20 feet, fromthe point of liquid hydrocarbon tially, the pores of this zone of thehydrocarbonproducing formation may be substantially saturated withwater, i.e., -90 percent occupied by water, particularly if the wellproduces almost percent water. It is preferred in the practice of thisinvention to reduce the water content of the pores of the formation tothe irreducible minimum for a substantial extent in the area surroundingthe location of fluid injection. Depending upon the geometricalconfiguration of the pores or interstices of the formation theirreducible minimum water content is usually in the range of 2-50percent of the pore range.

Prior to injecting the hot hydrocarbon oil into the formation one mayinject a slug of the hot hydrocarbon oil containing carbon dioxide, fluegases or other gases soluble in oil, up to the saturation amountdissolved therein into the lower part of the formation. The effectv toabout l,000 F, so as to substantially dry the formation into which thegas is injected. In another embodiment of this invention the injectedhot carbon dioxide or flue gases may contain a small amount (i.e., fromabout 200 to 5,000 parts per million) of a vaporized alkyl or alkyl-arylhalo silane which on hydrolysis deposits within the formation in thezone of the gas injection a film which is preferentially wettable byoil, e.g., a hydrophobic film. Suitable silanes include compounds of theformula:

R R'Si X,

wherein R and R are independently selected from the group consisting ofalkyl of from 1 to 6 inclusive carbon atoms and aryl of not more than 8carbon atoms and X is selected from the group consisting of chlorine,bromine and iodine, as exemplified by: methyldiethylchlorosilane,dimethyldichlorosilane, methyltrichlorosilane, dimethyldibromosilane,diethyldiiodosilane, dipropyldichlorosilane, dipropyldibromosilane,butyltrichlorosilane, .phenyltribromosilane, diphenyldichlorosilane,tolyltribromosilane, methylphenyldichlorosilane, etc. If desired, priorto injecting the hot hydrocarbon oil into the formation, a slug of thehydrocarbon oil containing dissolved therein one or more of thepreviously mentioned alkyl, aryl or alkyl-aryl halo silanes in an amountof from about 200 to 5,000 parts per million or more can be injectedinto the lower part of the formation.

Suitable hydrocarbon liquids which may be employed in the practice ofthis invention include crude oil substantiallly as produced fro the wellundergoing treatment, stock tank oil, normally liquid petroleumdistillate fractions, such as a gas oil or lubricating oil fraction,e.g., initial boiling point not less than 300 F, preferably not lessthan 400 F. The injection of a pctroleum liquid is preferred in thepractice of this invention since better displacement of the water isthereby obtained and there is less likelihood of channeling of theinjected hot liquid into the water-bearing or producing formation takingplace.

Referring now to FIG. 1 of the drawing which schematically illustratesthe water-coning phenomenon, a subsurface gaseous and/or liquidpetroleum hydrocabon-producing formation is indicated at 11. Animmediately underlying, substantially water saturated waterproducingformation is indicated at 12. A well bore 13 extends into thepetroleum-producing formation 11 and is bottomed in the water-producingformation 12. A production casing 14 is provided with perforations 15within the petroleum-producing formation 11. Under static conditions. orat a relatively low rate of petroleum production from the petroleumformation 11, the upper surface of the water-producing formation islocated at about he position indicated by the dashed line 16. Atrelatively high rates of production, and/or because of the upwarddirected pressure gradients associated with the flow of petroleum intoperforations 15, the water table rises to the extent it is balanced bythese upward directed pressure gradients. As the water table rises. asindicated by solid line 17, into the zone of production of liquidpetroleum hydrocarbons. water is produced by the lowermost perforations15 of casing 14. At still greater rates of production from formation 11,the water table continues to rise and there results a greater productionof water relative to the amount of produced petroleum. Theabove-described phenomenon is commonly known as water coning.

Referring now to H6. 2 of the drawing, there is schematicallyillustrated therein a method according to this invention for preventingand/or reducing water coning.

The same reference numerals have been employed in F IG. 2 as wereemployed in FIG. 1 for reasons of clarity and ease of understanding. Asindicated in FIG. 2, well bore 13 provided with casing 14 extends intopetroleum-producing formation 11 which overlays waterproducing formation12. In order to prevent and/or reduce water coning when the productionof petroleum is commenced or to purge the petroleum-producing formationof water which has invaded the petroleum producing formation 11 becauseof water coning, the casing 14 is perforated within thepetroleum-producing formation 11 near the top or upper surface thereofand near the bottom and/or in the upper part of the water producingformation 12, as illustrated. Packing 18 is then inserted within casing14 intermediate the upper and lower perforations 15. Dashed line 16indicates the normal interface of formations 11 and 12. After thepacking 18 has been installed, a hot fluid such as stock tank oil, ahigh boiling petroleum distillate fraction, at a temperature of about400 F is injected via conduit 19 into the formation 11 via the lowerperforations 15 in the casing 14 and removed from formation 11 via upperperforations 15 for recycle back into conduit 19 back to the surfacebetween conduit 19 and casing 14. The injection of the hot hydrocarboninto formation 11 is continued until the water has been displaced withinformation 11 for a substantial radial distance surrounding that portionof well bore 13 within formation 11, to the extent indicated by dashedline 21. After a sufficient amount of fluid has been injected todisplace the water from around the well bore 13 immediately adjacent theliquid petroleum-producing formation 11, the injection of fluid isdecreased and the production of petroleum from formation 11 iscommenced. As the liquid petroleum flows through perforations 15 intoproduction casing 14, upward-directed pressure gradients are createdwhich tend to lift the water table into the petroleum formation 11 inthe area of the well bore 13. Accordingly, the water present within thewaterproducing formation 12 tends to fill the spaces or pores offormation 11 from which it was displaced by the injected fluid. However,the flow of water thereinto is resisted because of the reducedpermeability of this localized portion of formation 11 due to thepresence of a substantial amount of injected fluid present in theinterstitial voids thereof. Due to the reduced permeability of this zoneconsiderable resistance to the flow of water therethrough is experiencedwith the result that the rate of petroleum production throughperforations it can be greatly increased without experiencing an undueamount of produced water due to water coning.

The practice of this invention is applicable not only to newly drilledwells but is also applicable to previously drilled wells which areproducing a considerable amount of water due to the phenomon of waterconing. In accordance 'with one preferred embodiment of this inventionparticularly applicable to previously drilled producing wells whichexhibit an unduly large amount of water production due to the phenomenonof water coning, the producing well is shut in for a period of timenecessary to approach or establish equilibrium conditions in thesubsurface producing formations. This period of time, depending uponvarious circumstances may be three hours to a month. Thereafter a hotliquid petroleum fraction is injected into and cycled within thehydrocarbon-producing formation as described hereinabove. After asufficient amount of liquid petroleum has been injected and cycled toforce the water in the petroleum-producing formation a substantialradial distance outwardly from the well bore the injection of liquidpetroleum is continued and petroleum production commenced. Thistechnique drastically changes the normal pressure gradients set uparound the well bore and prevents premature invasion or coning of waterinto the petroleum-producing formation. Obviously the injection rate ofthe recycled petroleum liquid would have to be less than the petroleum(oil and/or gas) production rate, as measured at the well head, thevolumes being expressed in reservoir volumes, so that there is a netproduction of petroleum from the formation.

What is claimed is:

l. A method of producing petroleum hydrocarbons and inhibiting waterconing during the production of petroleum hydrocarbons from a well borewhich penetrates a subsurface petroleum hydrocarbon-producing formationwhich is in contact with and overlays an adjacent water-producingformation which comprises:

a. injecting into the lower portion of the formation a slug of liquidhydrocarbon having a material selected from the group consisting ofcarbon dioxide and flue gases dissolved therein in amounts up to thesaturation value at the injection pressure,

b. injecting via said well bore a liquid hydrocarbonat a temperature ofabout 200 to about 500 F into the lower part of saidhydrocarbon-producing formation,

c. withdrawing via said well bore the injected liquid hydrocarbon fromthe upper portion of the hydrocarbon-producing formation, and

d. continuously injecting and withdrawing said liquid hydrocarbon whileat the same time producing via said well bore petroleum hydrocarbonsfrom the upper portion of the said hydrocarbon-bearing formation, thevolume of the liquid hydrocarbon injected being less than the volume ofthe withdrawn hydrocarbon plus the volume of the produced petroleumhydrocarbons, the volumes being expressed in reservoir or formationvolumes.

2. A method of producing petroleum hydrocarbons and inhibiting waterconing during the production of petroleum hydrocarbons from awell borewhich penetrates a subsurface petroleum hydrocarbon-producing formationwhich is in contact with and overlays an adjacent water-producingformation which comprises:

a. injecting into the lower portion of the formation a slug of liquidhydrocarbon having dissolved therein from about 200 to about 5,000 ppmof a hydrolyzable silane of the formula:

RR'SiX,

wherein R and R are independently selected from the group consisting ofalkyl of from i to 6 inclusive carbon atoms and aryl of not more than 8carbon atoms and X is selected from the group consisting of chlorine,bromine and iodine,

b. injecting via said well bore a liquid hydrocarbon at a temperature ofabout 200 to about 500 F into the lower part of saidhydrocarbon-producing formation,

c. withdrawing via said well bore the injected liquid hydrocarbon fromthe upper portion of the hydrocarbon-producing formation, and

d. continuously injecting and withdrawing said liquid hydrocarbon whileat the same time producing via said well bore petroleum hydrocarbonsfrom the upper portion of the said hydrocarbon-bearing formation, thevolume of the liquid hydrocarbon injected being less than the volume ofthe withdrawn liquid hydrocarbon plus the volume of the producedpetroleum hydrocarbons, the volumes being expressed in reservoir orformation volumes. 3. A method of producing petroleum hydrocarbons andinhibiting water coning during the production of petroleum hydrocarbonsfrom a well bore which penetrates a subsurface petroleumhydrocarbon-producing formation which is in contact with and overlays anadjacent water-producing formation which comprises:

a. injecting into the lower portion of the formation a slug of gasselected from the group consisting of carbon dioxide and flue gases at atemperature of about 200 to about l,000 F in an amount sufficient toreduce the water content of the formation into which the hot liquidhydrocarbon is injected to an amount below the so-called irreducibleminimum, the said carbon dioxide containing from about 200 to about5,000 ppm of a vaporized hydrolyzable silane of the formula:

R R Si X,

wherein R and R are independently selected from the group consisting ofalkyl of from 1 to 6 inclusive carbon atoms and aryl of not more than 8carbon atoms and X is selected from the group consisting of chlorine,bromine and iodine,

b. injecting via said well bore a liquid hydrocarbon at a temperature ofabout 200 to about 500 F into the lower part of saidhydrocarbon-producing formation,

c. withdrawing via said well bore the injected liquid hydrocarbon fromthe upper portion of the hydrocarbon-producing formation, and

d. continuously injecting and withdrawing said liquid hydrocarbon whileat the same time producing via said well bore petroleum hydrocarbonsfrom the upper portion of the saiclhydrocarbon-bearing formation, thevolume of the liquid hydrocarbon injected being less than the volume ofthe withdrawn liquid hydrocarbon plus the volume of the producedpetroleum hydrocarbons, the volumes being

1. A METHOD OF PRODUCING PETROLEUM HYDROCARBONS AND INHIBITING WATERCONING DURING THE PRODUCTION OF PETROLEUM HYDROCARBONS FROM A WELL BOREWHICH PENETRATES A SUBSURFACE PETROLEUM HYDROCARBON-PRODUCING FORMATIONWHICH IS IN CONTACT WITH AND OVERLAYS AN ADJACENT WATER-PRODUCINGFORMATION WHICH COMPRISES: A. INJECTING INTO THE LOWER PORTION OF THEFORMATION A SLUG OF LIQUID HYDROCARBON HAVING A MATERIAL SELECTED FROMTHE GROUP CONSISTING OF CARBON DIOXIDE AND FLUE GASES DISSLOVED THEREININ AMOUNTS UP TO THE SATURATION VALUE AT THE INJECTION PRESSURE, B.INJECTING VIA SAID WELL BORE A LIQUID HYDROCARBON AT A TEMPERATURE OFABOUT 200* TO ABOUT 500*F INTO THE LOWER PART OF SAIDHYDROCARBON-PRODUCING FORMATION, C. WITHDRAWING VIA SAID WELL BORE THEINJECTED LIQUID HYDROCARBON FROM THE UPPER PORTION OF THEHYDROCARBONPRODUCING FORMATION, AND D. CONTINUOUSLY INJECTING ANDWITHDRAWING SAID LIQUID HYDROCARBON WHILE AT THE SAME TIME PRODUCING VIASAID WELL BORE PERTROLUEM HYDROCARBONS FROM THE UPPER PORTION OF THESAID HYDROCARBON-BEARING FORMATION, THE VOLUMN OF THE LIQUID HYDROCARBONINJECTED BEING LESS THAN THE VOLUME OF THE WITHDRAW HYDROCARBON PLUS THEVOLUME OF THEPRODCED PETROLEUM HYDROCARBONS, THE VOLUMES BEING EXPRESSEDIN RESERVOIR OR FORMATION VOLUMES.
 2. A method of producing petroleumhydrocarbons and inhibiting water coning during the production ofpetroleum hydrocarbons from a well bore which penetrates a subsurfacepetroleum hydrocarbon-producing formation which is in contact with andoverlays an adjacent water-producing formation which comprises: a.injecting into the lower portion of the formation a slug of liquidhydrocarbon having dissolved therein from about 200 to about 5,000 ppmof a hydrolyzable silane of the formula: R R'' Si X, wherein R and R''are independently selected from the group consisting of alkyl of from 1to 6 inclusive carbon atoms and aryl of not more than 8 carbon atoms andX is selected from the group consisting of chlorine, bromine and iodine,b. injecting via said well bore a liquid hydrocarbon at a temperature ofabout 200* to about 500* F into the lower part of saidhydrocarbon-producing formation, c. withdrawing via said well bore theinjected liquid hydrocarbon from the upper portion of thehydrocarbon-producing formation, and d. continuously injecting andwithdrawing said liquid hydrocarbon while at the same time producing viasaid well bore petroleum hydrocarbons from the upper portion of the saidhydrocarbon-bearing formation, the volume of the liquid hydrocarboninjected being less than the volume of the withdrawn liquid hydrocarbonplus the volume of the produced petroleum hydrocarbons, the volumesbeing expressed in reservoir or formation volumes.
 3. A method ofproducing petroleum hydrocarbons and inhibiting water coning during theproduction of petroleum hydrocarbons from a well bore which penetrates asubsurface petroleum hydrocarbon-producing formation which is in contactwith and overlays an adjacent water-producing formation which comprises:a. injecting into the lower portion of the formation a slug of gasselected from the group consisting of carbon dioxide and flue gases at atemperature of about 200 to about 1,000* F in an amount sufficient toreduce the water content of the formation into which the hot liquidhydrocarbon is injected to an amount below the so-called irreducibleminimum, the said carbon dioxide containing from about 200 to about5,000 ppm of a vaporized hydrolyzable silane of the formula: R R'' Si X,wherein R and R'' are independently selected from the group consistingof alkyl of from 1 to 6 inclusive carbon atoms and aryl of not more than8 carbon atoms and X is selected from the group consisting of chlorine,bromine and iodine, b. injecting via said well bore a liquid hydrocarbonat a temperature of about 200* to about 500* F into the lower part ofsaid hydrocarbon-producing formation, c. withdrawing via said well borethe injected liquid hydrocarbon from the upper portion of thehydrocarbon-producing formation, and d. continuously injecting andwithdrawing said liquid hydrocarbon while at the same time producing viasaid well bore petroleum hydrocarbons from the upper portion of the saidhydrocarbon-bearing formation, the volume of the liquid hydrocarboninjected being less than the volume of the withdrawn liquid hydrocarbonplus the volume of the produced petroleum hydrocarbons, the volumesbeing expressed in reservoir or formation volumes.